The present disclosure relates to a light emitting device, and more particularly, to a light emitting device that may emit a white light having various color temperatures by using a few white light sources.
A light emitting diode LED is a highly efficient and environmentally-friendly light source and is taking center stage in various fields. For example, the LED is being used in many fields such as a display device, a car, and general lighting. In particular, a demand for a white-light emitting device implementing a white light is gradually increasing.
A phosphor in the LED functions as a medium that changes energy of an excitation source to energy of a visible light and the efficiency of the phosphor is an important element associated directly with the efficiency of a display product.
There is a light emitting device using a blue LED as one of light emitting devices emitting a white light. The light emitting device using the blue LED uses a blue light as an excitation source to apply a yellow phosphor emitting a yellow light to a LED emitting a blue light, so the blue light emitted from the blue LED is mixed with the yellow light emitted from the yellow phosphor to implement a white color.
That is, the light emitting device emitting the white light uses a method of applying a YAG:Ce phosphor showing a yellow color to the blue LED to obtain the white light, as a method of applying a phosphor to the blue LED to use a blue light emitted from the blue LED and a second light source emitted from the phosphor.
There are limitations in that the method involves quantum deficits resulting from using the second light and efficiency decrease resulting from re-emission efficiency and color rendering is not easy. Thus, since a typical white-light emitting device is implemented by combining the blue LED and the yellow phosphor, it lacks green and red components and thus it is difficult to express natural colors. Thus, the typical white-light emitting device is being limitatively applied to the screen of a portable phone or notebook computer. Nevertheless, it has been widely used because it is easy to operate and remarkably cheap.
A light emitting device needs to control or change the color temperature of emitted light but the typical light emitting device has a limitation in that it is difficult to control the color temperature of light emitted by using a few white light sources.